Micro-cellular closed-cell sponge rubber outers

ABSTRACT

The invention relates to a method of making an outer tire layer on a pneumatic tire microcellular closed-cell sponge rubber, method of making the aforesaid product.

FIELD OF THE INVENTION

[0001] The field of the present invention is rubber outer layers, andspecifically micro-cellular closed-cell sponge rubber outer layers forpneumatic tires, shoe soles and other applications.

BACKGROUND OF THE INVENTION

[0002] According to conventional philosophies, pneumatic rubber tireouters are made exclusively of a relatively hard durable solid rubber.However, the characteristics of relatively hard non-sponge (“solid”)rubber do not favorably support the special needs of certain sportsvehicles, such as mountain bikes, bicycle motorcross (“bmx”) vehicles,cross-country bicycles, All Terrain Vehicles (“ATV”), and go-carts.Similarly, the characteristics of relatively hard solid rubber do notfavorably support the needs of certain other types of special vehicles,including for example, wheelchairs, baby joggers, skateboards,rollerblades, scooters, motorcross vehicles, and others.

[0003] Pneumatic mountain bicycle tire outers have conventionally beenmade with relatively hard durable solid rubber. Relatively hard durablesolid rubber is used in making the outers for such tires under theconventional thinking that because a mountain biking tire is subjectedto high-friction conditions, the characteristics of relatively harddurable solid rubber will provide long wear.

[0004] There are a number of problems, however, with such tires. Forexample, relatively hard solid rubber does not have a high-frictioncoefficient—in most cases, the harder the rubber, the lower the frictioncoefficient of the rubber. Therefore, most conventional relatively hardsolid rubber tires do not provide good traction characteristics.

[0005] Another problem with pneumatic tires made with relatively hardsolid rubber outers is that they do not exhibit good shock absorptioncharacteristics. In the case of mountain bikes, shock absorption is acritical factor in the design of such bikes. Mountain bikes can cost tentimes the amount of a regular street bicycle—much of the cost beingdevoted to providing highly-advanced shock absorption characteristics tovarious structural features of the bicycle. After spending thousands ofdollars on a highly-advanced shock absorbing bike frame, the mountainbiker then mounts pneumatic tires made of relatively hard solid rubberthat characteristically exhibit low shock-dampening characteristics—thatis, they bounce.

[0006] Soft rubber exhibits higher-friction coefficient characteristicsthan harder rubber. However, soft rubber does not wear well and furtherdoes not exhibit significantly reduced dampening characteristics ascompared to harder rubber.

[0007] Sponge rubber exhibits high-dampening and high-frictioncoefficient characteristics. However, a sponge rubber made using verysoft rubber would not exhibit durability characteristics necessary forpneumatic tires.

[0008] As with pneumatic tire rubber outers, rubber outers, that is, anouter layer of rubber, in other applications that are often subjected tohigh-wear, high-friction conditions, such as, for example, shoe soleouters, are often made with relatively hard durable solid rubberaccording to the conventional thinking that the relatively hard durablesolid rubber will provide long wear. However, as with tires, shoe soleouters (outsoles) and other rubber outers made according to thisconventional thinking do not exhibit high-friction coefficient orshock-absorbing characteristics.

SUMMARY OF THE INVENTION

[0009] The present invention provides a method for formulating withrelatively hard solid rubber, a micro-cellular closed-cell sponge rubberouter such as for use as an outer tire layer (a “tire outer”) onpneumatic tires or for use as a component of shoe sole outers, saidmethod comprising blowing a relatively hard non-sponge (or “solid”)rubber having a first hardness scale measurement with a micro-cellularclosed-cell inducing blowing agent to produce a micro-cellularclosed-cell sponge rubber with a second hardness scale measurement,wherein the second hardness scale measurement is less than the firsthardness scale measurement.

[0010] The term “outer” is used herein to mean an outer layer. In thecase of pneumatic tires, an outer layer of rubber (a tire “outer”) isbonded to a non-stretch or limited-stretch pneumatic tire lining. In thecase of shoe soles, an outer layer of shoe sole material (a shoe soleouter, sometimes referred to in the shoe industry as an outsole) isfastened or vulcanized to a shoe upper, or is fastened or vulcanized toa midsole and shoe upper. The way in which a tire outer is fastened to apneumatic tire lining is not a limitation of the present invention. Theway in which a shoe sole outer is fastened or vulcanized to a shoeupper, or to a midsole and shoe upper, or to any other inner-sole,midsole, and shoe upper configuration is not a limitation of the presentinvention.

[0011] The words “non-sponge” and “solid” are used interchangeably inthe disclosure of this invention. It will be understood by someone withordinary skill in the art that blowing a relatively hard non-spongesolid rubber with a micro-cellular closed-cell inducing blowing agentwill produce a micro-cellular closed-cell rubber having higher dampeningcharacteristics and a higher friction coefficient than the solid rubberfrom which the sponge rubber is produced. An outer tire layer soformulated would be for use on pneumatic tires for any of a variety ofvehicles, including but not limited to: mountain bikes, cross-countrybicycles, All Terrain Vehicles (“ATV”), off-road vehicles, go-carts,wheelchairs, baby joggers, skateboards, rollerblades, scooters,motorcross vehicles, and others.

[0012] The present invention also provides a method for manufacturingpneumatic rubber tires, said method comprising vulcanizing an outer tirelayer of micro-cellular closed-cell sponge rubber formulated fromrelatively hard non-sponge rubber, and bonding the outer tire layer to anon-stretch or limited-stretch pneumatic tire lining. Pneumatic tirelinings, often made of nylon material, are sometimes referred to as“non-stretch.” However, it will be understood by someone with ordinaryskill in the art of tire making that nylon and other pneumatic tirelining material “stretch” to a limited extent. Therefore, referenceherein to “non-stretch” or “limited-stretch” pneumatic tire liningmaterial means pneumatic tire lining material, such as nylon, thatstretches only to a limited extent.

[0013] The present invention also provides a method for manufacturingpneumatic rubber tires, said method comprising vulcanizing an outer tirelayer comprising micro-cellular closed-cell sponge rubber formulatedfrom relatively hard non-sponge rubber, said outer tire layer furthercomprising non-sponge rubber, and bonding the outer tire layer to anon-stretch or limited-stretch pneumatic tire lining.

[0014] The present invention provides a method for manufacturingpneumatic rubber tires, said method comprising molding an outer tirelayer of micro-cellular closed-cell sponge rubber formulated fromrelatively hard non-sponge rubber, and bonding the molded outer tirelayer to a non-stretch or limited-stretch pneumatic tire lining.

[0015] The present invention further provides a method for manufacturingpneumatic rubber tires, said method comprising bonding an outer tirelayer of micro-cellular closed-cell sponge rubber formulated fromrelatively hard non-sponge rubber to a non-stretch or limited-stretchpneumatic tire lining.

[0016] The present invention further provides a method for manufacturingpneumatic rubber tires, said method comprising bonding an outer tirelayer comprising micro-cellular closed-cell sponge rubber formulatedfrom relatively hard non-sponge rubber and further comprising non-spongerubber, to a non-stretch or limited-stretch pneumatic tire lining. Thepresent invention also provides a pneumatic rubber tire, said pneumaticrubber tire comprising an outer tire layer comprising micro-cellularclosed-cell sponge rubber formulated from relatively hard non-spongerubber wherein the outer tire layer is bonded to a non-stretch, orlimited-stretch, pneumatic tire lining.

[0017] The present invention also provides a pneumatic rubber tire, saidpneumatic rubber tire comprising an outer tire layer comprisingmicro-cellular closed-cell sponge rubber formulated from relatively hardnon-sponge rubber and further comprising non-sponge rubber wherein theouter tire layer is bonded to a non-stretch, or limited-stretch,pneumatic tire lining.

[0018] The present invention further provides a method for manufacturingshoe sole outers, said method comprising vulcanizing micro-cellularclosed-cell sponge rubber formulated from relatively hard non-spongerubber with non-sponge rubber in a shoe sole outer mold.

[0019] The present invention further provides a shoe sole outer (alsosometimes referred to as an outsole), said shoe sole outer comprisingmicro-cellular closed-cell sponge rubber formulated from relatively hardnon-sponge rubber and further comprising non-sponge rubber.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] These and other features of the present invention are more fullyset forth in the following description of exemplary embodiments of theinvention. The description is presented with reference to theaccompanying drawings in which:

[0021]FIG. 1 is a high level flow diagram depicting the logic steps todetermining a proportion of blowing and a rubber formulation with whichto manufacture a rubber for a particular intended purpose;

[0022]FIG. 2 is a graphic representation that depicts, under extrememagnification, an exemplary uneven density distribution of gas pocketsthat sometimes results from micro-cellular, closed-cell sponge rubbervulcanization;

[0023]FIG. 3 is a cross-sectional view of an exemplary outer tire moldinto which rubber is placed to form a tire outer in an exemplaryembodiment of the present invention;

[0024]FIG. 4 is a cross-sectional view of an exemplary single-rubbertire outer in which micro-cellular closed-cell sponge rubber forms atire outer in an exemplary single-rubber tire outer embodiment of thepresent invention;

[0025]FIG. 5 is a cross-sectional view of an exemplary multi-rubber tireouter in which non-sponge rubber forms outer tire tread lugs andmicro-cellular closed-cell sponge rubber forms inner tire tread lugs ina first exemplary multi-rubber tire outer embodiment of the presentinvention;

[0026]FIG. 6 is a cross-sectional view of an exemplary multi-rubber tireouter in which non-sponge rubber forms inner tire tread lugsmicro-cellular closed-cell sponge rubber forms outer tire tread lugs ina second exemplary multi-rubber tire outer embodiment of the presentinvention;

[0027]FIG. 7 is a cross-sectional view of an exemplary assembled bicycletire comprising a multi-rubber tire outer in a first alternativeexemplary embodiment of the present invention;

[0028]FIG. 8 is a top view of an exemplary shoe mold;

[0029]FIG. 9 is a cross-sectional view of a portion of the exemplaryshoe mold;

[0030]FIG. 10 is a cross-sectional view of a portion of an exemplaryshoe sole outer comprising micro-cellular closed-cell sponge rubber andnon-sponge rubber; and

[0031]FIG. 11 is a bottom view of an exemplary shoe sole outercomprising micro-cellular closed-cell sponge rubber and non-spongerubber.

DETAILED DESCRIPTION OF THE INVENTION

[0032] The making of sponge rubber is well known in the art of rubbermaking. One of a variety of “blowing agents” is used in the rubberformulation process to create a multitude of gas pockets in the finalrubber product.

[0033] Instead of using soft rubber, according to the present invention,blowing agents are added to relatively hard solid rubber formulations tocreate a relatively hard rubber sponge rubber. The relatively hardrubber sponge rubber is then used to make an outer tire layer forpneumatic tires. The exemplary description of methods of formulatingrelatively hard rubber sponge rubber for, and manufacturing, a mountainbike tire is illustrative and is not a limitation of the invention.

[0034] Various blowing agents provide different types of results.Proportions being equal, some blowing agents tend to create a smallernumber of, but large-sized, air or gas pockets; whereas other blowingagents tend to create a higher number of, but smaller-sized air or gaspockets.

[0035] Some blowing agents produce what is known in the art as “opencell” sponge. Such blowing agents produce air pockets that are open.Such open air pockets can be useful when the rubber is intended forwater absorption products.

[0036] Other blowing agents produce what is known as “closed cell”sponge. Such blowing agents produce gas pockets in rubber such that eachgas pocket is encapsulated with the rubber.

[0037] The present invention provides that blowing agents that producemicro-cellular, closed-cell sponge are used to “blow” relatively hardsolid rubber. The book entitled Blue Book 1997: Materials, compoundingingredients, machinery and services for the rubber industry, Job H.Lippincott publisher, published by Rubber World magazine, a Lippincott &Peto publication, contains a list of rubber blowing agents on pages312-318, the factual content of which is incorporated by referenceherein for all purposes as if fully stated here and selected portions ofthe factual content of which are provided below.

[0038] The Blue Book lists a number of blowing agents by Tradename,composition and Supplier; properties and function and compounding aredescribed for each blowing agent listed. The Blue Book list of BlowingAgents is extensive. Accordingly, exemplary blowing agent compositionsare identified below. The following list of exemplary micro-cellular,closed-cell sponge inducing blowing agent compositions is illustrativeand is not a limitation of the blowing agents that can be used in thepresent invention.

[0039] Exemplary blowing agent compositions listed in the Blue Book thatproduce microcellular, closed-cell sponge include: Azodicarbonamide(including Activated and Modified forms), p-toluene sulfonylhydrazide(TSH), Sodium bicarbonate and Dinitroso pentamethylene tetramine (DNPT).Someone with ordinary skill in the art of rubber making will understandthat use of other micro-cellular, closed-cell sponge inducing blowingagent compositions is possible without deviating from the spirit of theinvention. Someone with ordinary skill in the art of rubber making willfurther understand that considerations for selection of a blowing agentinclude the form (dust, paste, etc.) preferred, and the temperature forvulcanizing a particular rubber formulation. Further, the function andcompounding requirements are specific to each blowing agent composition,and to some extent, to each formulation marketed under the respectiveTradenames listed in the Blue Book. Someone with ordinary skill in theart of rubber making will understand the blowing agent-specific functionand compounding requirements.

[0040] The Blue Book identifies a number of Tradenames under whichActivated Azodicarbonamide can be purchased, including, among others:Celogen 754 (Uniroyal Chemical, supplier), Celogen 785A (UniroyalChemical, supplier), and Celogen 700 (Uniroyal Chemical, supplier). TheBlue Book identifies a number of Tradenames under which Azodicarbonamidecan be purchased, including, among others: Celogen AZ (UniroyalChemical, supplier), Expancel AZ (Proquitec Industrie, supplier),Porofor ADC/F (Bayer Fibers, Organics & Rubber Division, supplier),Porofor ADC/M (Bayer Fibers, Organics & Rubber Division, supplier), andUnicell D (Dong Jin (USA), supplier). The Blue Book identifies a numberof Tradenames under which Modified Azodicarbonamide can be purchased,including, among others: Ficel (Schering Berlin, supplier) and UnicellDX (Dong Jin (USA), supplier). The Blue Book, page 316, identifies theProperties of one Azodicarbonamide composition, marketed under theTradename of Porofor ADC/M as: “SP gr. 1.6. Yellow powder. Decompositiontemp. not below 205° C. Volume of gas released about 220 ml/g.” The BlueBook, page 316, identifies the Function and Compounding of Porofor ADC/Mas: “A nitrogen liberating blowing agent for the manufacture ofodorless, cellular vulcanizates. Especially suitable for the manufactureof articles to be cured at relatively high temperatures (e.g.microcellular profiles in LCM devices).”

[0041] The Blue Book identifies a number of Tradenames under whichp-toluene sulfonylhydrazide can be purchased, including, among others:Biofoam SH (Rit-Chem supplier); Celogen TSH (Uniroyal Chemical,supplier); Expencel TSH (Proquitec Industira, supplier); and Unicell H(Dong Jin (USA), supplier). The Blue Book, page 314, describes theproperties for one of the preceding exemplary TSH blowing agentcompositions (Celogen TSH) as: “Sp gr. 1.42. Cream colored crystallinepowder. Melting point, 125-150° C. (257-302° F.). Decomposition range,110-120° C. (230-250° F.). Amount of nitrogen gas, 115 cc/gm STP.” TheBlue Book, page 314, further describes the function and compounding forone of the preceding exemplary TSH blowing agent compositions (CelogenTSH) as: “A low temperature blowing agent for NR, SBR, NBR, LLR, CR andsilicone rubber. Nitrogen blowing agent; produces odorless cellularrubber goods; nondiscoloring and nonstaining; slightly activating to thecure. Celogen TSH is a superior blowing agent for the expansion ofliquid polysulfide rubbers at room temp.”.

[0042] The Blue Book identifies a number of Tradenames under whichSodium bicarbonate can be purchased, including, among others: Dynacarb(Littlem Corporation, supplier). The Blue Book, page 314, describes theproperties for Dynacarb as: “Sp gr. 2.18 free flowing, non-dusting finewhite powder.” The Blue Book, page 314, describes the function andcompounding for Dynacarb as: “Small particle size for sponge compounds.”

[0043] The Blue Book identifies a number of Tradenames under whichDinitroso pentamethylene tetramine (DNPT) can be purchased, including,among others: Opex (Uniroyal Chemical, supplier), and Unicell G (DongJin (USA), supplier). The Blue Book, page 316, describes the propertiesfor Opex as: “DNPT on an inert carrier—80% active. Pale yellow powder.Opex is flanunable and should be kept away from all sources of heat,open flame and sparks. Strong acids and acidic salts will cause rapiddecomposition of Opex. Incompatible with oxidizing and reducing agents.”The Blue Book, page 314, describes the function and compounding for Opexas: “Especially effective in pressure procured closed cell applicationsof SBR, CR, NBR and EPDM. Also, imparts a fine cellular structure inextrusion processes. At cure temperature of 130° C. (288° F.) andhigher. Opex and some of its decompositon products show a definite cureactivation in both natural and synthetic rubber sponge. Used in themanufacture of open and closed cell sponge in a wide range of densitieswith uniform cell structure.”

[0044] The proportion of the blowing agent used and the particularrubber formulation used determines the final dampening and frictioncoefficient characteristics of the sponge rubber produced. Performancecharacteristics desirable for an intended use of the rubber to beproduced directs the proportion of the blowing agent and the particularrubber formulation to be used.

[0045] The hardness of rubber can be measured with a device known in theart as a “durometer.” A standard hardness scale known in the art is the“Shore A” scale. In an exemplary embodiment of the invention, a rubberwith a hardness of approximately 65 to 70 on the Shore A scale is blownwith a micro-cellular, closed-cell sponge inducing blowing agent untilthe resulting sponge rubber has a hardness of approximately 35 to 40 onthe Shore A scale.

[0046]FIG. 1 is a high level flow diagram depicting the logic steps todetermining a proportion of blowing and a rubber formulation with whichto manufacture a rubber for a particular intended purpose. The presentinvention provides for determining 1 a set of performancecharacteristics desirable for an intended use of a pneumatic rubbertire, said set of performance characteristics comprising a resiliencyfactor, a dampening factor, and a relative hardness factor. Then arubber formulation is determined 2 that exhibits a level of rubberresiliency corresponding to said resiliency factor. A blown rubberformulation is then determined 3 that would have a level of dampeningcorresponding to said dampening factor and a hardness measurementcorresponding to said relative hardness factor. The determined rubberformulation is then blown 4 with a micro-cellular, closed-cell spongeinducing blowing agent to produce the blown rubber formulation having alevel of dampening corresponding to said dampening factor and a hardnessmeasurement corresponding to said relative hardness factor. Rubbers thatcould be used would include SBR rubber (a synthetic “natural” rubberavailable from various suppliers), Stealth grade C4 (Supplier: Stone AgeEquipment, Inc., Redlands, California, USA), Stealth grade S1 (Supplier:Stone Age Equipment, Inc., Redlands, Calif., USA), and natural rubber(available from various suppliers).

[0047] In one exemplary outer tire layer embodiment, blowing agentCelogen AZ (Uniroyal Chemical, supplier) is used to blow Stealth gradeC4 (Supplier: Stone Age Equipment, Inc., Redlands, Calif., USA) rubberwith a hardness of approximately 79 on the Shore A scale down to ahardness of approximately 40 on the Shore A scale. In a second exemplaryouter tire layer embodiment, blowing agent Celogen AZ (UniroyalChemical, supplier) is used to blow Stealth grade S1 (Supplier: StoneAge Equipment, Inc., Redlands, Calif., USA) rubber with a hardness ofapproximately 72 down to a hardness of approximately 40 on the Shore Ascale. In a third outer tire layer embodiment, blowing agent Celogen AZ(Uniroyal Chemical, supplier) is used to blow SBR rubber (a synthetic“natural” rubber available from various suppliers) with a hardness ofapproximately 70 on the Shore A scale down to a hardness ofapproximately 40 on the Shore A scale.

[0048] For example, in the case of downhill mountain bike racing, atire, according to the invention, a micro-cellular, closed-cell spongeinducing blowing agent is used to blow a relatively hard, lowresilience, high dampening rubber to create an outer tire layer ofmicrocellular, closed-cell sponge. In an exemplary embodiment of adownhill mountain bike racing tire, a rubber with a hardness ofapproximately 60 to 65 on the Shore A scale is blown with amicro-cellular, closed-cell sponge inducing blowing agent until theresulting sponge rubber has a hardness of approximately 30 to 35 on theShore A scale. Then, according to the invention, the outer tire layer isbonded to a non-stretch or limited-stretch pneumatic tire lining.Non-stretch, or limited-stretch, pneumatic tire linings are often madeof nylon. Techniques for bonding a rubber layer to a non-stretch, orlimited-stretch, nylon pneumatic tire lining are well known in the artof tire making.

[0049] In the case of cross-country bicycle racing, a tire with lowrolling resistance is desirable. According to the invention, amicro-cellular, closed-cell sponge inducing blowing agent is used toblow a relatively hard, higher resiliency rubber to create an outer tirelayer of micro-cellular, closed-cell sponge. In an exemplary embodimentof a cross-country bicycle racing tire, a rubber with a hardness ofapproximately 70 to 75 on the Shore A scale is blown with amicro-cellular, closed-cell sponge inducing blowing agent until theresulting sponge rubber has a hardness of approximately 40 to 45 on theShore A scale. Then, according to the invention, the outer tire layer isbonded to a non-stretch, or limited stretch, pneumatic tire lining.

[0050] In the case of wet surface cycling, it is desirable to maximizesurface contact. According to the invention, a micro-cellular,closed-cell sponge inducing blowing agent is used to blow a relativelyhard non-sponge rubber to a lower level of hardness on the Shore Ascale. The result is a sponge rubber with a higher density ofmicro-cellular closed-cell gas pockets. In an exemplary embodiment of awet surface cycling tire, a rubber with a hardness of approximately 60to 65 on the Shore A scale is blown with a micro-cellular, closed-cellsponge inducing blowing agent until the resulting sponge rubber has ahardness of approximately 30 to 35 on the Shore A scale. Then, accordingto the invention, the outer tire layer is bonded to a non-stretch, orlimited-stretch, pneumatic tire lining.

[0051] As part of the vulcanization process for a micro-cellular,closed-cell sponge made according to the present invention, a “skin”will sometimes form on the outer surface of the rubber. Such a skinsometimes has fewer micro-cellular, closed-cell sponge gas pockets thanrubber farther from the surface. FIG. 2 depicts, under extrememagnification, an uneven distribution of gas pockets. FIG. 2 depicts areduction in the density of gas pockets from the interior 5 of therubber, to the exterior 6 of the rubber in an exemplary micro-cellular,closed-cell sponge rubber vulcanization process. In some otheralternative micro-cellular, closed-cell sponge rubber vulcanizationprocesses, the density of gas pockets is more or less evenlydistributed.

[0052]FIG. 3 is a cross-sectional view of an exemplary outer tire mold10-10′ into which rubber is placed to form a tire outer in an exemplaryembodiment of the present invention. As depicted in FIG. 3, a typicaltire mold comprises two separate pieces, e.g., 10 and 10′, that areplaced together. In an exemplary single-rubber outer embodiment of thepresent invention, micro-cellular closed-cell sponge rubber is placed inthe mold to form a tire outer. As one with ordinary skill in the rubberarts will understand, pre-cured rubber is clay-like. To form a tireouter, rubber is placed in a mold, is pressed so that the rubber “flows”into the mold, and is then cured in a vulcanization process.

[0053]FIG. 4 is a cross-sectional view of an exemplary single-rubbertire outer 20 in which micro-cellular closed-cell sponge rubber 80 formsa tire outer in an exemplary single-rubber tire outer embodiment of thepresent invention. As depicted in FIG. 4, as will be understood bysomeone with ordinary skill in the bicycle tire-making art, a bead,e.g., 30 and 31, such as one made with Kevlar or other aramid fiber, isinserted in the rubber placed in the mold 10 (FIG. 3). Further, asdepicted in FIG. 3, the exemplary mold 10 provides detents 14 with whichto form tire outer protrusions, e.g., 32 and 33 as depicted in FIGS. 4through 7.

[0054] Additional modifications and variations of the above-describedembodiments will be apparent to those with ordinary skill in the artwithout departing from the spirit of the invention. For example, it willbe understood by someone with ordinary skill in the art that, withoutdeparting from the spirit of the invention, an outer tire layercomprising multiple types of rubber, each type of rubber provided in oneor more particular areas of the outer surface of the tire, can be madeusing vulcanization. FIG. 5 is a cross-sectional view of an exemplarymulti-rubber tire outer 40 in which hard, non-sponge rubber 60 formsouter tire tread lugs, 70-71 respectively, and micro-cellularclosed-cell sponge rubber 80 forms inner tire tread lugs 50 in a firstexemplary multi-rubber tire outer embodiment of the present invention.

[0055] To form the exemplary multi-rubber tire outer 40 depicted in FIG.5, micro-cellular closed-cell sponge rubber 80 would be placed in theinner tire tread lug indentations 11 of the exemplary outer tire mold 10as depicted in FIG. 3; hard, non-sponge rubber 60 would be placed in theouter tire tread lug indentations 12 of the exemplary outer tire mold 10as depicted in FIG. 3. The rubber in the mold would then be cured usingvulcanization. The rubbers comprising the micro-cellular closed-cellsponge rubber 80 and the hard, non-sponge rubber 60 would be selectedaccording to criteria known in the art such that the two rubbers 80 and60 would knit together forming long chains of molecules.

[0056] One selection criteria for selecting the two rubbers 80 and 60that would knit together would be to blow rubber having the samecomposition as the non-sponge rubber 60 with a micro-cellularclosed-cell inducing blowing agent to produce the micro-cellularclosed-cell sponge rubber 80.

[0057]FIG. 6 is a cross-sectional view of an exemplary multi-rubber tireouter 100 in which hard, non-sponge rubber 60 forms inner tire treadlugs 50 and in which micro-cellular closed-cell sponge rubber 80 formsouter tire tread lugs 70-71 in a second exemplary multi-rubber tireouter embodiment of the present invention.

[0058] Once a tire outer, e.g., 20, 40, 100 has been formed according tothe present invention, the tire outer, e.g., 20, 40, 100 is bonded to anon-stretch or limited-stretch pneumatic tire lining. The resultingbonded tire assembly 200 as depicted in FIG. 7 can be assembled withother parts, e.g., a tire rim 120 to form a bicycle tire 300 as depictedin FIG. 7. FIG. 7 is a cross-sectional view of an exemplary assembledbicycle tube tire 300 comprising a multi-rubber tire outer 40 bonded toa pneumatic tire lining to form a bonded tire assembly 200 in the firstalternative exemplary embodiment of the present invention. As depictedin FIG. 7, a tube 140 is filled with air to inflate the outer bondedtire assembly 200. In a tubeless pneumatic tire (not pictured), air usedto inflate the outer bonded tire assembly 200 is sealed between the rim120 and the tire outer protrusions 32 and 33.

[0059] The present invention further provides a method for manufacturingshoe sole outers, e.g., 220 as shown in FIGS. 10-11. The presentinvention further provides a shoe sole outer, e.g., 220 that is made byvulcanizing micro-cellular closed-cell sponge rubber 222 (as depicted inFIGS. 10-11) formulated from relatively hard non-sponge rubber withnon-sponge rubber 221 (as depicted in FIGS. 10-11) in a shoe sole outermold 210 (as depicted in FIGS. 8-9).

[0060]FIG. 8 is a top view of an exemplary shoe mold and FIG. 9 is across-sectional view of a portion of the exemplary shoe mold. In a waysimilar to that described above for placing clay-like uncured rubber ina tire mold, uncured solid rubber would be placed in the shoe sole“tread” indentations 201 in the mold 200; uncured micro-cellularclosed-cell sponge rubber would be placed in the shoe sole mold 200 ontop of the previously placed uncured solid rubber. The rubber would thenbe pressed to flow into the mold. The molded shoe outer would then becured using vulcanization so that non-sponge solid rubber would “kniftwith the micro-cellular closed cell sponge rubber. FIG. 10 is across-sectional view of a portion of an exemplary shoe sole outercomprising micro-cellular closed-cell sponge rubber and non-spongerubber. FIG. 11 is a bottom view of an exemplary shoe sole outercomprising micro-cellular closed-cell sponge rubber and non-spongerubber. In an exemplary shoe sole outer embodiment, blowing agentCelogen AZ (Uniroyal Chemical, supplier) is used to blow Stealth gradeS1 (Supplier: Stone Age Equipment, Inc., Redlands, Calif., USA) rubberwith a hardness of approximately 72 down to a hardness of approximately50 on the Shore A scale.

[0061] In an alternative exemplary shoe sole outer embodiment, uncuredmicro-cellular closed-cell sponge rubber would be placed in the shoesole “tread” indentations 201 in the mold 200; uncured solid rubberwould be placed in the shoe mold 200 on top of the previously placeduncured micro-cellular closed-cell sponge rubber.

[0062] Illustrative Embodiments

[0063] Although the present invention has been described in certainspecific embodiments, many additional modifications and variations wouldbe apparent to those skilled in the art. It is, therefore, to beunderstood that this invention may be practiced otherwise than asspecifically described. Thus, the embodiments of the present inventiondescribed herein should be considered in all respects as illustrativeand not restrictive, the scope of the invention to be determined by theappended claims and their equivalents rather than the foregoingdescription.

What is claimed is:
 1. A method for manufacturing a tire outer forpneumatic tires consisting of microcellular closed-cell sponge rubbermade from relatively hard solid rubber, said method comprising: blowinga relatively hard solid rubber having a first hardness scale measurementwith a micro-cellular closed-cell inducing blowing agent to produce amicro-cellular closed-cell sponge rubber, wherein the second hardnessscale measurement is less than the first hardness scale measurement; andvulcanizing as a tire outer for pneumatic tires the micro-cellularclosed-cell sponge rubber formulated from relatively hard solid rubber.2. A method for manufacturing pneumatic rubber tires, said methodcomprising: vulcanizing a tire outer comprising a first plurality oftire tread lugs consisting of microcellular closed-cell sponge rubberformulated from relatively hard solid rubber; and bonding the tire outerto a limited-stretch pneumatic tire lining.
 3. The method of claim 2,wherein said tire outer further comprising a second plurality of tiretread lugs consisting of non-sponge rubber.
 4. A method formanufacturing pneumatic rubber tires, said method comprising: molding atire outer consisting of micro-cellular closed-cell sponge rubberformulated from relatively hard solid rubber; and bonding the moldedtire outer to a limited-stretch pneumatic tire lining.
 5. A method formanufacturing pneumatic rubber tires, said method comprising: bonding atire outer comprising a first plurality of tire tread lugs consisting ofmicrocellular closed-cell sponge rubber formulated from relatively hardsolid rubber to a limited-stretch pneumatic tire lining.
 6. The methodof claim 5 wherein said tire outer further comprising a second pluralityof tire tread lugs consisting of non-sponge rubber.
 7. A pneumaticrubber tire, said pneumatic rubber tire comprising: a tire outerconsisting of micro-cellular closed-cell sponge rubber formulated fromrelatively hard solid rubber wherein the tire outer is bonded to alimited-stretch pneumatic tire lining.
 8. A pneumatic rubber tire, saidpneumatic rubber tire comprising: a tire outer comprising a firstplurality of tire tread lugs consisting of non-sponge rubber and asecond plurality of tire tread lugs consisting of micro-cellularclosed-cell sponge rubber formulated from relatively hard solid rubber;said tire outer bonded to a limited-stretch pneumatic tire lining.
 9. Amethod for manufacturing a tire outer for pneumatic rubber tires, saidmethod comprising: vulcanizing a tire outer comprising a first pluralityof tire tread lugs comprising microcellular closed-cell sponge rubberformulated from relatively hard solid rubber, said tire outer furthercomprising a second plurality of tire tread lugs comprising non-spongerubber.
 10. The method of claim 9 wherein the first plurality of tiretread lugs are inner tire tread lugs and wherein the second plurality oftire tread lugs are outer tire tread lugs.
 11. A tire outer forpneumatic rubber tires, said tire outer consisting of: micro-cellularclosed-cell sponge rubber formulated from relatively hard solid rubber.12. A tire outer for pneumatic rubber tires, said tire outer comprising:a first plurality of tire lugs consisting of micro-cellular closed-cellsponge rubber formulated from relatively hard solid rubber; and a secondplurality of tire tread lugs consisting of non-sponge rubber.
 13. Amethod for making a tire outer comprising micro-cellular closed-cellsponge rubber, said method comprising: determining a set of performancecharacteristics desirable for an intended use of a pneumatic rubbertire, said set of performance characteristics comprising a resiliencyfactor, a dampening factor, and a relative hardness factor; determininga rubber formulation having a level of rubber resiliency correspondingto said resiliency factor; determining a blown rubber formulation havinga level of dampening corresponding to said dampening factor; determininga blown rubber formulation having a hardness measurement correspondingto said relative hardness factor; blowing said determined rubberformulation with a micro-cellular closed-cell inducing blowing agent toproduce the blown rubber formulation having a level of dampeningcorresponding to said dampening factor and a hardness measurementcorresponding to said relative hardness factor; and vulcanizing the tireouter for pneumatic tires comprising a plurality of tire tread lugsconsisting of micro-cellular closed-cell sponge rubber formulated fromrelatively hard solid rubber.
 14. A method for manufacturing shoe soleouters, said method comprising: blowing a relatively hard solid rubberwith a micro-cellular closed-cell inducing blowing agent to produce anuncured micro-cellular closed-cell sponge rubber; placing the uncuredmicro-cellular closed-cell sponge rubber in a plurality of shoe soletread lug indentations of a shoe sole outer mold; placing uncured solidnon-sponge rubber over the uncured micro-cellular closed-cell spongerubber in the shoe sole outer mold; and vulcanizing said micro-cellularclosed-cell sponge rubber with non-sponge rubber in the shoe sole outermold.
 15. A method for manufacturing shoe sole outers, said methodcomprising: blowing a relatively hard solid rubber with a micro-cellularclosed-cell inducing blowing agent to produce an uncured micro-cellularclosed-cell sponge rubber; placing uncured solid non-sponge rubber in aplurality of shoe sole tread lug indentations of a shoe sole outer mold;placing the uncured micro-cellular closed-cell sponge rubber over theuncured solid non-sponge rubber in the shoe sole outer mold; andvulcanizing said micro-cellular closed-cell sponge rubber withnon-sponge rubber in the shoe sole outer mold.
 16. A shoe sole outer,said shoe sole outer comprising. micro-cellular closed-cell spongerubber; and a plurality of tread lugs comprising solid non-spongerubber.
 17. A shoe sole outer, said shoe sole outer comprising:micro-cellular closed-cell sponge rubber vulcanized in a shoe sole outermold with non-sponge rubber tread lugs.
 18. A shoe, said shoecomprising: a shoe upper; and a shoe sole outer, said shoe sole outercomprising micro-cellular closed-cell sponge rubber and a plurality oftread lugs comprising non-sponge rubber.
 19. A shoe, said shoecomprising: a shoe upper; and a shoe sole outer, said shoe sole outercomprising non-sponge rubber and a plurality of tread lugs comprisingmicro-cellular closed-cell sponge rubber.